Apo and calcium-bound crystal structures of cytoskeletal protein alpha-14 giardin (annexin E1) from the intestinal protozoan parasite Giardia lamblia.
Apo and calcium-bound crystal structures of cytoskeletal protein alpha-14 giardin (annexin E1) from the intestinal protozoan parasite Giardia lamblia.
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来自肠道原生动物寄生虫蓝氏贾第鞭毛虫的细胞骨架蛋白 α-14 贾第素（膜联蛋白 E1）的 Apo 和钙结合晶体结构。
DOI：
10.1016/j.jmb.2008.11.012
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发表时间：
2009
影响因子：
5.6
通讯作者：
Luecke,Hartmut
中科院分区：
文献类型：
--
作者：
Pathuri,Puja;Nguyen,EmilyTam;Ozorowski,Gabriel;Svard,StaffanG;Luecke,Hartmut
α-14贾第鞭毛虫蛋白（膜联蛋白E1）是膜联蛋白α贾第鞭毛虫蛋白家族的成员，已被证明定位于肠道原生动物寄生虫贾第鞭毛虫的鞭毛。α贾第蛋白显示与膜联蛋白的共同祖先，膜联蛋白是一个蛋白质家族，其中大多数以Ca 2+依赖性方式与磷脂和细胞膜结合，并参与许多膜相关过程，包括细胞骨架重排和膜组织。已经提出α-14贾第虫素可能在贾第虫分化期间的细胞骨架重排中起重要作用。为了更好地了解α-14贾丁的作用模式及其生物学作用，我们确定了α-14贾丁的三维结构及其磷脂结合特性。在这里，我们报告的载脂蛋白晶体结构的α-14贾第丁确定在两种不同的晶体形式，以及钙离子结合的晶体结构的α-14贾第丁，细化到1.9，1.6和1.65 μ m，分别。虽然α-14贾丹的整体折叠类似于α-11贾丹，但需要多波长异常色散定相来解决α-14贾丹结构，这表明α贾丹家族的这两个成员之间存在显着的结构差异。与大多数膜联蛋白结构（通常具有N-末端结构域）不同，α-14贾第虫素仅由核心结构域组成，随后是C-末端延伸，其可作为与贾第虫中细胞骨架蛋白伴侣结合的配体。在Ca 2+结合的结构中，我们检测到五个结合的钙离子，其中之一是一个新的，高度协调的钙结合位点，以前没有观察到的膜联蛋白结构。这种新型的高亲和力钙结合位点由七个蛋白质供体基团组成，这是晶体结构中很少观察到的特征。此外，磷脂结合试验表明，α-14贾第丁表现出钙依赖性结合磷脂，协调细胞骨架拆卸/组装过程中的寄生虫。
Alpha-14 giardin (annexin E1), a member of the alpha giardin family of annexins, has been shown to localize to the flagella of the intestinal protozoan parasite Giardia lamblia. Alpha giardins show a common ancestry with the annexins, a family of proteins most of which bind to phospholipids and cellular membranes in a Ca2+-dependent manner and are implicated in numerous membrane-related processes including cytoskeletal rearrangements and membrane organization. It has been proposed that alpha-14 giardin may play a significant role during the cytoskeletal rearrangement during differentiation of Giardia. To gain a better understanding of alpha-14 giardin's mode of action and its biological role, we have determined the three-dimensional structure of alpha-14 giardin and its phospholipid-binding properties. Here, we report the apo crystal structure of alpha-14 giardin determined in two different crystal forms as well as the Ca2+-bound crystal structure of alpha-14 giardin, refined to 1.9, 1.6 and 1.65 Å, respectively. Although the overall fold of alpha-14 giardin is similar to that of alpha-11 giardin, multiwavelength anomalous dispersion phasing was required to solve the alpha-14 giardin structure, indicating significant structural differences between these two members of the alpha giardin family. Unlike most annexin structures, which typically possess N-terminal domains, alpha-14 giardin is composed of only a core domain, followed by a C-terminal extension that may serve as a ligand for binding to cytoskeletal protein partners in Giardia. In the Ca2+-bound structure we detected five bound calcium ions, one of which is a novel, highly coordinated calcium-binding site not previously observed in annexin structures. This novel high-affinity calcium-binding site is composed of seven protein donor groups, a feature rarely observed in crystal structures. In addition, phospholipid-binding assays suggest that alpha-14 giardin exhibits calcium-dependent binding to phospholipids that coordinate cytoskeletal disassembly/assembly during differentiation of the parasite.